The present invention is generally directed to encapsulated toner compositions, and more specifically the present invention is directed to colored encapsulated toner compositions formulated by interfacial polymerization processes. Thus, in one embodiment the present invention is directed to cold pressure fixable toner compositions comprised of readily available, and economical colored pigments encapsulated within a polymeric shell obtained by interfacial polymerization processes. The aforementioned toner compositions are useful for permitting the development of images in electrostatographic systems, inclusive of electrostatic imaging processes wherein pressure fixing, especially pressure fixing in the absence of heat, is selected.
Encapsulated, and cold pressure fixable toner compositions are known. Cold pressure fixable toners have a number of advantages as compared to toners that are fused by heat, primarily relating to the requirements for less energy since these toner compositions can be fused at room temperature. Nevertheless, many of the prior art cold pressure fixable toner compositions suffer from a number of deficiencies. For example, these toner compositions must usually be fused under high pressure, which has a tendency to severely disrupt the fusing characteristics of the toner selected. This can result in images of low resolution, or no images whatsoever. Also, with some of the prior art cold pressure toner compositions substantial image smearing can result from the high pressures required and from the use of plasticizer type materials in large quantities. Additionally, the cold pressure fixing toner compositions of the prior art have other disadvantages in that, for example, these compositions when used for development cause in some instances images with high gloss that are of low crease resistance. Furthermore, the images resulting exhibit an undesirable carbon paper effect, thus there is a total or partial image transfer from the image substrate to neighboring substrates caused by pressures arising from normal handling. In contrast, images developed with the cold pressure compositions prepared in accordance with the process of the present invention possess a low gloss appearance on plain paper, and further there is no carbon paper effect observed. Also, the toner compositions prepared in accordance with the process of the present invention have hard shells thus enabling images of excellent resolution with substantially no background deposits.
With further reference to the prior art, there is disclosed in U.S. Pat. No. 4,307,169 microcapsular electrostatic marking particles containing a pressure fixable core, and an encapsulating substance comprised of a pressure rupturable shell wherein the shell, such as a polyamide is formed by an interfacial polymerization. Furthermore, there is disclosed in U.S. Pat. No. 4,407,922 pressure sensitive toner compositions obtained by interfacial polymerization processes, and comprised of a blend of two immiscible polymers selected from the group consisting of certain polymers as a hard component, and polyoctyldecylvinylether-co-maleic anhydride as a soft component.
Examples of patents illustrating color photocapsule toners are U.S. Pat. Nos. 4,399,209; 4,482,624; 4,483,912; and 4,397,483. More specifically, the U.S. Pat. No. 4,397,483 illustrates encapsulated toner materials which have applications in very specific areas such as pressure sensitive recording paper. Capsules prepared for this application are usually coated on a substrate directly from the emulsion in which they are prepared and withstand difficult spray drying processes, a disadvantage alleviated with the toners prepared in accordance with the process of the present invention. Furthermore, these capsules contain an organic liquid in the core which, when used in a dry development system, could result in poor fix properties. Also, the range of particle sizes prepared by the aforementioned process results in the formation of pressure sensitive recording particles which are usually not acceptable for electrostatographic development systems. In the U.S. Pat. Nos. 4,399,209, 4,482,624 and 4,483,912 there are described toner compositions with costly encapsulated radiation sensitive components thereby necessitating the need for an image forming agent. Further, contrary to the process of the present invention, wherein the cold pressure fixable toner composition can be developed and imaged on plain paper, imaging using capsules illustrated in these Patents require paper or other appropriate substrates which have been treated by an acid developer, for example.
With further reference to the prior art, there is disclosed in U.S. Pat. No. 4,476,211 the preparation of electrostatographic toner materials with surface electroconductivity. Specifically, there is disclosed in the U.S. Pat. No. 4,476,211 a cold pressure fixable toner composition with polyamide, polyurea and other types of shell materials prepared by an interfacial polymerization process. The colorant selected for these compositions is generally comprised of a variety of dyes or pigments, and the core contains a polymeric material with a binder therein for retaining the colorant within the core and assisting in the fixing of the the colorant onto the surface of a support medium. Examples of high boiling liquids selected for the process of the U.S. Pat. No. 4,476,211 include those boiling at temperatures higher than 180.degree. C. such as phthalic esters, phosphoric acid esters, and alkylnaphthalenes.
Moreover, illustrated in a copending application U.S. Ser. No. 621,307, the disclosure of which is totally incorporated herein by reference, are single component cold pressure fixable toner compositions, wherein the shell selected can be prepared by an interfacial polymerization process. A similar teaching is present in copending application U.S. Ser. No. 718,676 relating to cold pressure fixable toners, the disclosure of which is totally incorporated herein by reference. In the aforementioned application, the core can be comprised of magnetite and a polyisobutylene of a specific molecular weight encapsulated in a polymeric shell material generated by an interfacial polymerization process.
Accordingly, there is a need for improved colored encapsulated toner compositions. Also, there is a need for colored encapsulated toner compositions containing therein inexpensive pigments, such as printing ink substances. There is also a need for colored cold pressure fixable toner compositions with economical newsprint colorants therein. Additionally, there is a need for simple economical polymerization processes that will permit the generation of encapsulated cold pressure fixable toner compositions, especially compositions with hard shells. There is also a need for improved processes that will enable cold pressure fixable toner compositions with hard shells, and wherein the monomer selected for the shell is dissolved in the core.